Every single feeling of perception – of touch, of smell, of color – can be traced back to a particular set of neurons.

Stimulate those neurons directly and a person’s perception of reality can be controlled.

In the 1940s, neurosurgeon Wilder Penfield experimented with the brains of his patients. He sent mild electric shocks to their somatosensory cortex.

As a result, they felt as if their body was being touched even when it wasn’t. A shock to one area, a feeling of their arm being pushed, a shock to another and a feeling of their upper lip being nipped.

Science fiction takes brain stimulation technology to its extreme – fully immersive virtual reality. Want the user to feel as if he’s actually boxing, not just waving his hands in the air? Sense his arm and body movements. Then stimulate the neurons responsible for his fist and arm when he gives a hit and the neurons responsible for his head and nose when he takes one.